Changing Background Colour

I am using the Eighties Theme in ww.wp.xz.cn on http://innovatecreateeducate.dreamhosters.com/wp-admin/

I want to change the look globally to a black background to replicate http://www.innovatecreateeducate.com – my other site – I am looking to move it to ww.wp.xz.cn – but have been unable to get the black background.

Can anyone help?

I’m a bit of an novice here!

Thanks,

Paul